For their study, the researchers assessed the contribution of each of six modifiable lifestyle factors and their combined effects on memory among thousands of participants over 10 years.
The six healthy lifestyle factors included a healthy diet, regular physical exercise, active social contact, active cognitive activity, and an avoidance of smoking and alcohol.
Each factor was assigned a calculation standard. For example, for participants to have a healthy diet, their daily intake had to consist of at least seven to 12 food items including vegetables, meat and dairy products.
At least 150 minutes of moderate or 75 minutes of vigorous activity per week was deemed to be sufficient as a healthy level of physical exercise for the study, which ran from 2009 to 2019.
The researchers enrolled nearly 30,000 participants with normal cognitive function and a mean age of 72 from 12 provinces in the north, south and west of China. Their memory function was assessed using the widely used Auditory Verbal Learning test.
They were also tested for the most prevalent genetic risk factor for Alzheimer’s disease and related dementias, which was found in 20 per cent of those taking part.
The participants were categorised according to their lifestyle choices, with those reporting at least four healthy factors grouped as favourable. The average group had two to three factors, while those scoring zero or one were placed in the unfavourable grouping.
The researchers found that over the life of the study, participants in the favourable group had slower memory decline compared with the unfavourable grouping, but so did those carrying the Alzheimer’s genetic marker.
Although carriers of the genotype experienced faster memory loss, those with favourable and average lifestyles had a slower rate of decline than the unfavourable group.
A healthy diet had the strongest effect on slowing memory decline, followed by cognitive activity and then physical exercise, the researchers said.
“These results provide an optimistic outlook, as they suggest that although genetic risk is not modifiable, a combination of more healthy lifestyle factors is associated with a slower rate of memory decline, regardless of the genetic risk,” they said.
The study’s co-author Serge Gauthier, emeritus professor in neurology and neurosurgery at McGill University in Canada, said an important finding was that people with a moderate genetic risk of dementia could reduce age-associated cognitive decline with a combination of healthy lifestyle habits.
“Basic, epidemiological and clinical research conducted by leading researchers has a positive impact on the health of persons living in China and worldwide,” Gauthier said.
Although the study focused on age-associated memory decline, “it was possible but not yet proven that enhancing a combination of healthy lifestyle habits does indeed lower the number of persons with dementia”, he said.
Gauthier, who described the study as “significant”, said there was likely to be a need to reduce other risk factors – such as high blood pressure and diabetes – to achieve a significant level of prevention against dementia.
